Purely anecdotally, I put a 65mm ultraprime on a Sony A7 to grab some photos the other day. I was really amazed how sharp they were, zooming in and in on the picture until I was just looking at pixels. I would say subjectively speaking they comfortably resolved the resolution of an A7. Whatever that is.

You can’t really speak about lenses in terms of “K’s” of resolution because resolution is dependent on sensor size and pixel pitch, which varies greatly from camera to camera. A lens that covers and performs well on a large format camera,
for example, may not look as good on a camera with a smaller sensor because you’re not using the whole image circle the lens projects – just a smaller portion of the center.

To properly answer your question, we’d need to know what camera you intend to put the lenses on and what sensor mode / frame lines you intend to use on that camera.

For what it’s worth, when dealing with Super35-sensor cameras I’ve seen many 2nd/VFX units on big-budget features take Ultra Primes because of their sharpness and lack of distortion. The 20mm Ultra Prime seems to be the go-to
lens for many VFX plate arrays when tiling multiple S35 cameras (frequently Alexa Minis or Red Weapons) together to form a single large plate image.

A well-maintained set of Ultra Primes will consistently hit 200 lines per millimeter (the typical way of quantifying lens sharpness) at the center at a T2 for most focal lengths, and many can get there at the edges of a Super35 image circle
if you stop down to a T2.8 or T4.

All this being said, in the motion picture optics world there’s a clear trend of moving AWAY from sharp lenses for principal photography such that there’s now a brisk business around the world in companies buying up decades-old “vintage”
optics with less-than-perfect optical characteristics and rehousing them for cinematography use. As with anything, it depends upon application and personal taste.

You can’t really speak about lenses in terms of “K’s” of resolution because resolution is dependent on sensor size and pixel pitch, which varies greatly from camera to camera. A lens that covers and performs well on a large format camera,
for example, may not look as good on a camera with a smaller sensor because you’re not using the whole image circle the lens projects – just a smaller portion of the center.

To properly answer your question, we’d need to know what camera you intend to put the lenses on and what sensor mode / frame lines you intend to use on that camera.

For what it’s worth, when dealing with Super35-sensor cameras I’ve seen many 2nd/VFX units on big-budget features take Ultra Primes because of their sharpness and lack of distortion. The 20mm Ultra Prime seems to be the go-to
lens for many VFX plate arrays when tiling multiple S35 cameras (frequently Alexa Minis or Red Weapons) together to form a single large plate image.

A well-maintained set of Ultra Primes will consistently hit 200 lines per millimeter (the typical way of quantifying lens sharpness) at the center at a T2 for most focal lengths, and many can get there at the edges of a Super35 image circle
if you stop down to a T2.8 or T4.

All this being said, in the motion picture optics world there’s a clear trend of moving AWAY from sharp lenses for principal photography such that there’s now a brisk business around the world in companies buying up decades-old “vintage”
optics with less-than-perfect optical characteristics and rehousing them for cinematography use. As with anything, it depends upon application and personal taste.

The 90% spec I believe you’re referring to is >90% of MTF at 10 lines per millimeter, which says more about contrast (which is also important in terms of apparent sharpness) than it does resolving power.

When I say 200 lines per millimeter I’m talking about the ability of the lens to reproduce a test pattern of line pairs of that density either when projected on a lens projector or when photographing a resolution test chart such that the
individual lines are still visible as alternating white and black lines and not blurred to a gray field.

This graphic may help illustrate (thanks to Cooke for having this resource available at a meaningful resolution on their website):

If you look at the line pair test targets the smallest lines are 200 per millimeter – that’s referring to the actual density of lines as printed on the test reticle. The boxes / lines on reticle refer to various imaging format sizes.

When evaluating a lens on a lens projector, typically you look at how many line pairs the lens can resolve at various distances from the center of field out to the limits of the imager size onto which the lens will be focusing an image.
A sharp lens might be able to reproduce the 200 lines per millimeter target, whereas a less-sharp lens would blur that target to gray such that you might need to look at the 140 or 100 or even lower density targets before you could make out the individual
lines. Most modern cine lenses can hit 200 lines per millimeter at the center, though many will need to stop down a bit to hit that target at the edges of a Super35 frame if they can do so at all. If you look at an older lens like a Lomo Anamorphic they
won’t hit 200 lines ANYWHERE.

The 200 lines per millimeter standard goes back to the film days and was about as sharp as you needed any lens to be, though admittedly as pixel densities continue to climb it may be necessary to use even finer test targets.

Back to your original question, the fact that they can hit that target means Ultra Primes are pretty sharp. Master Primes are even sharper and can meet that target at wider stops, but at a tradeoff of being larger, heavier, and more expensive.
Leica Summilux-C’s are pretty sharp too. If you don’t care about having a cine-friendly form factor with expanded focus scales for following focus, Zeiss Otus stills lenses are also very sharp. In terms of zooms, Fuji Premieres are probably the sharpest
on the market. As for whether any of them are sharp enough for 8K on a Helium, how sharp is sharp enough? That’s a subjective question only you can answer by testing. IMHO Ultra Primes are decently high-performing in terms of sharpness and contrast. Your
own mileage may vary.

The 90% spec I believe you’re referring to is >90% of MTF at 10 lines per millimeter, which says more about contrast (which is also important in terms of apparent sharpness) than it does resolving power.

When I say 200 lines per millimeter I’m talking about the ability of the lens to reproduce a test pattern of line pairs of that density either when projected on a lens projector or when photographing a resolution test chart such that the
individual lines are still visible as alternating white and black lines and not blurred to a gray field.

This graphic may help illustrate (thanks to Cooke for having this resource available at a meaningful resolution on their website):

If you look at the line pair test targets the smallest lines are 200 per millimeter – that’s referring to the actual density of lines as printed on the test reticle. The boxes / lines on reticle refer to various imaging format sizes.

When evaluating a lens on a lens projector, typically you look at how many line pairs the lens can resolve at various distances from the center of field out to the limits of the imager size onto which the lens will be focusing an image.
A sharp lens might be able to reproduce the 200 lines per millimeter target, whereas a less-sharp lens would blur that target to gray such that you might need to look at the 140 or 100 or even lower density targets before you could make out the individual
lines. Most modern cine lenses can hit 200 lines per millimeter at the center, though many will need to stop down a bit to hit that target at the edges of a Super35 frame if they can do so at all. If you look at an older lens like a Lomo Anamorphic they
won’t hit 200 lines ANYWHERE.

The 200 lines per millimeter standard goes back to the film days and was about as sharp as you needed any lens to be, though admittedly as pixel densities continue to climb it may be necessary to use even finer test targets.

Back to your original question, the fact that they can hit that target means Ultra Primes are pretty sharp. Master Primes are even sharper and can meet that target at wider stops, but at a tradeoff of being larger, heavier, and more expensive.
Leica Summilux-C’s are pretty sharp too. If you don’t care about having a cine-friendly form factor with expanded focus scales for following focus, Zeiss Otus stills lenses are also very sharp. In terms of zooms, Fuji Premieres are probably the sharpest
on the market. As for whether any of them are sharp enough for 8K on a Helium, how sharp is sharp enough? That’s a subjective question only you can answer by testing. IMHO Ultra Primes are decently high-performing in terms of sharpness and contrast. Your
own mileage may vary.

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